Plant signaling & behavior (Plant Signal Behav)

Publications in this journal

• Article: A9C sensitive Cl- - accumulation in A. thaliana root cells during salt stress is controlled by internal and external calcium

  Livia Saleh, Christoph Plieth
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  ABSTRACT: The involvement of chloride in salt stress symptoms and salt tolerance mechanisms in plants has been less investigated in the past. Therefore, we studied the salt-induced chloride influx in Arabidopsis expressing the GFP-based anion indicator Clomeleon. High salt concentrations induce two phases of chloride influx. The fast kinetic phase is likely caused by membrane depolarization, and is assumed to be mediated by channels. This is followed by a slower “saturation” phase, where chloride is accumulated in the cytoplasm. Both phases of chloride uptake are dependent on the presence of external calcium. In general: with high [Ca2+] less chloride is accumulated in the cytoplasm. Surprisingly, also the internal calcium availability has an impact on chloride transport. A complete block of the second phase of chloride influx is achieved by the anion channel blocker A9C and trivalent cations (La3+, Gd3+, and Al3+). Other channel blockers and diuretics were found to inhibit the process partially. The results suggest that several transporter species are involved here and a part of chloride possibly enters the cells through cation channels after salt application.
  Plant signaling & behavior 06/2013;
• Article: Herbivory of maize by southern corn rootworm induces expression of the major intrinsic protein ZmNIP1;1 and leads to the discovery of a novel aquaporin ZmPIP2;8.

  Susan D Lawrence, Nicole G Novak, Hao Xu, Janice E K Cooke
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  ABSTRACT: Aquaporins channel water and other neutral molecules through cell membranes. Aquaporin gene expression is subject to transcriptional control and can be modulated by factors affecting water balance such as salt, abscisic acid and drought. During infestation of maize by southern corn rootworm (SCR), an insect that chews into and significantly damages maize roots, three maize aquaporins were differentially expressed upon prolonged infestation. Using a brief infestation of maize roots ZmNIP1;1 transcript abundance again increased under infestation while expression of a new aquaporin, ZmPIP2;8 and ZmTIP2;2 expression did not change. Since ZmPIP2;8 has not been described previously, the deduced protein sequence was analyzed in silico and found to contain the hallmarks of plant aquaporins, with a predicted protein structure similar to other functionally characterized PIP2s. NIPs characterized to date have been implicated in facilitating the movement of a variety of small molecules, while TIPs and PIPs often have the capacity to facilitate trans-membrane movement of water. Functional assays (using heterologous expression in Xenopus laevis oocytes) of ZmTIP2;2 and ZmPIP2;8 confirmed that these aquaporins demonstrate water channel capacity.
  Plant signaling & behavior 05/2013; 8(8).
• Article: Optimizing stem-loop qPCR assays through multiplexed cDNA synthesis of U6 and miRNAs.

  Marie Turner, Sajag Adhikari, Senthil Subramanian
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  ABSTRACT: We recently reported that hairpin (or stem-loop) priming is better-suited than polyA tailing to generate cDNA for plant microRNA qPCR. One major limitation of this method is the need to perform individual cDNA synthesis reactions for the reference gene and test miRNAs. Here, we report a novel fusion primer that allows multiplexed hairpin cDNA synthesis of the most-commonly used reference gene, nucleolar small RNA U6, together with test miRNAs. We also propose the use of miR1515 as a house keeping control for tropical legumes. We show that multiplexed cDNA synthesis does not result in loss of sensitivity and reduces the amount of RNA required for miRNA gene expression assays.
  Plant signaling & behavior 05/2013; 8(8).
• Article: The key gluconeogenic enzyme fructose-1,6-bisphosphatase is secreted during prolonged glucose starvation and is internalized following glucose re-feeding via the non-classical secretory and internalizing pathways in Saccharomyces cerevisiae.

  Bennett J Giardina, Hui-Ling Chiang
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  ABSTRACT: In Saccharomyces cerevisia, the key gluconeogenic enzyme fructose-1,6-bisphosphatase is secreted into the periplasm during prolonged glucose starvation and is internalized into Vid/endosomes following glucose re-feeding. Fructose-1,6-bisphosphatase does not contain signal sequences required for the classical secretory and endocytic pathways. Hence, the secretion and internalization are mediated via the non-classical pathways.
  Plant signaling & behavior 05/2013; 8(8).
• Article: Assessing the regulation of leaf redox status under water stress conditions in Arabidopsis thaliana: Col-0 ecotype (wild-type and vtc-2), expressing mitochondrial and cytosolic roGFP1.

  Ricard Brossa, Marta Pinto, Keni Jiang, Leonor Alegre, Lewis J Feldman
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  ABSTRACT: Using Arabidopsis plants Col-0 and vtc2 transformed with a redox sensitive green fluorescent protein, (c-roGFP) and (m-roGFP), we investigated the effects of a progressive water stress and re-watering on the redox status of the cytosol and the mitochondria. Our results establish that water stress affects redox status differently in these two compartments, depending on phenotype and leaf age, furthermore we conclude that ascorbate plays a pivotal role in mediating redox status homeostasis and that Col-0 Arabidopsis subjected to water stress increase the synthesis of ascorbate suggesting that ascorbate may play a role in buffering changes in redox status in the mitochondria and the cytosol, with the presumed buffering capacity of ascorbate being more noticeable in young compared with mature leaves. Re-watering of water-stressed plants was paralleled by a return of both the redox status and ascorbate to the levels of well-watered plants. In contrast to the effects of water stress on ascorbate levels, there were no significant changes in the levels of glutathione, thereby suggesting that the regeneration and increase in ascorbate in water-stressed plants may occur by other processes in addition to the regeneration of ascorbate via the glutathione. Under water stress in vtc2 lines it was observed stronger differences in redox status in relation to leaf age, than due to water stress conditions compared with Col-0 plants. In the vtc2 an increase in DHA was observed in water-stressed plants. Furthermore, this work confirms the accuracy and sensitivity of the roGFP1 biosensor as a reporter for variations in water stress-associated changes in redox potentials.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Arabidopsis thaliana : Proliferating cell nuclear antigen 1 and 2 possibly form homo- and hetero-trimeric complexes in the plant cell.

  Wojciech Strzalka, Chhavi Aggarwal
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  ABSTRACT: The proliferating cell nuclear antigen (PCNA) is a key component of the eukaryotic DNA replication machinery. It also plays an important role in DNA repair mechanisms. Despite the intense scientific research on yeast and human PCNA, information describing the function of this protein in plants is still very limited. In the previous study Arabidopsis PCNA2 but not PCNA1 was proposed to be functionally important in DNA polymerase η-dependent postreplication repair. In addition to the above study, PCNA2 but not PCNA1 was also shown to be necessary for Arabidopsis DNA polymerase λ-dependent oxidative DNA damage bypass. Taking into account the reported differences between PCNA1 and PCNA2, we tested the idea of a possible cooperation between PCNA1 and PCNA2 in the plant cell. In a bimolecular fluorescence complementation assay an interaction between PCNA1 and PCNA2 was observed in the nucleus, as well as in the cytoplasm. This finding, together with our previous results, indicates that PCNA1 and PCNA2 may cooperate in planta by forming homo- and heterotrimeric rings. The observed interaction might be relevant when distinct functions for PCNA1 and PCNA2 are considered.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Does chemical aposematic (warning) signaling occur between host plants and their potential parasitic plants?

  Simcha Lev-Yadun
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  ABSTRACT: Aposematism (warning) signaling is a common defensive mechanism toward predatory or herbivorous animals, i.e., interactions between different trophic levels. I propose that it should be considered at least as a working hypothesis that chemical aposematism operates between certain host plants and their plant predators, parasitic plants, and that although they are also plants, they belong to a higher trophic level. Specific host plant genotypes emit known repelling chemical signals toward parasitic plants, which reduce the level of, slow the directional parasite growth (attack) toward the signaling hosts, or even cause parasitic plants to grow away from them in response to these chemicals. Chemical potential host aposematism toward parasitic plants may be a common but overlooked defense from parasitic plants.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Cis- and trans-zeatin differentially modulate plant immunity.

  Dominik Großkinsky, Kerstin Edelsbrunner, Hartwig Pfeifhofer, Eric van der Graaff, Thomas Roitsch
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  ABSTRACT: Phytohormones are essential regulators of various processes in plant growth and development. Several phytohormones are also known to regulate plant responses to environmental stress and pathogens. Only recently, cytokinins have been demonstrated to play an important role in plant immunity. Increased levels of cytokinins such as trans-zeatin, which are considered highly active, induced resistance against mainly (hemi)biotrophic pathogens in different plant species. In contrast, cis-zeatin is commonly regarded as a cytokinin exhibiting low or no activity. Here we comparatively study the impact of both zeatin isomers on the infection of Nicotiana tabacum by the (hemi)biotrophic microbial pathogen Pseudomonas syringae. We demonstrate a biological effect of cis-zeatin and a differential effect of the two zeatin isomers on symptom development, defense responses and bacterial multiplication.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Arabidopsis sos1 mutant in a salt-tolerant accession revealed an importance of salt acclimation ability in plant salt tolerance.

  Hirotaka Ariga, Taku Katori, Ryouhei Yoshihara, Yoshihiro Hase, Shigeki Nozawa, Issay Narumi, Satoshi Iuchi, Masatomo Kobayashi, Kenji Tezuka, Yoichi Sakata, Takahisa Hayashi, Teruaki Taji
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  ABSTRACT: An analysis of the salinity tolerance of 354 Arabidopsis thaliana accessions showed that some accessions were more tolerant to salt shock than the reference accession, Col-0, when transferred from 0 to 225 mM NaCl. In addition, several accessions, including Zu-0, showed marked acquired salt tolerance after exposure to moderate salt stress. It is likely therefore that Arabidopsis plants have at least two types of tolerance, salt shock tolerance and acquired salt tolerance. To evaluate a role of well-known salt shock tolerant gene SOS1 in acquired salt tolerance, we isolated a sos1 mutant from ion-beam-mutagenized Zu-0 seedlings. The mutant showed severe growth inhibition under salt shock stress owing to a single base deletion in the SOS1 gene and was even more salt sensitive than Col-0. Nevertheless, it was able to survive after acclimation on 100 mM NaCl for 7 d followed by 750 mM sorbitol for 20 d, whereas Col-0 became chlorotic under the same conditions. We propose that genes for salt acclimation ability are different from genes for salt shock tolerance and play an important role in the acquisition of salt or osmotic tolerance.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Small changes in ambient temperature affect alternative splicing in Arabidopsis thaliana.

  Corinna Streitner, Craig G Simpson, Paul Shaw, Selahattin Danisman, John W S Brown, Dorothee Staiger
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  ABSTRACT: Alternative splicing (AS) gives rise to multiple mRNA isoforms from the same gene, providing possibilities to regulate gene expression beyond the level of transcription. In a recent paper in Nucleic Acids Research we used a high resolution RT-PCR based panel to study changes in AS patterns in plants with altered levels of an hnRNP-like RNA-binding protein in Arabidopsis thaliana. Furthermore, we detected significant changes in AS patterns between different Arabidopsis ecotypes. Here we investigated how small changes in ambient temperature affect AS. We found significant changes in AS for 12 of 28 investigated events (43%) upon transfer of Arabidopsis plants from 20°C to 16°C and for 6 of the 28 investigated events (21%) upon transfer from 20°C to 24°C.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Complexity of potassium acquisition: How much flows through channels?

  Devrim Coskun, Herbert J Kronzucker
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  ABSTRACT: The involvement of potassium (K (+) )-selective, Shaker-type channels, particularly AKT1, in primary K (+) acquisition in roots of higher plants has long been of interest, particularly in the context of low-affinity K (+) uptake, at high K (+) concentrations, as well as uptake from low-K (+) media under ammonium (NH 4 (+) ) stress. We recently demonstrated that K (+) channels cannot mediate K (+) acquisition in roots of intact barley (Hordeum vulgare L.) seedlings at low (22.5 µM) external K (+) concentrations ([K (+) ]ext) and in the presence of high (10 mM) external NH 4 (+) , while the model species Arabidopsis thaliana L. utilizes channels under comparable conditions. However, when external NH 4 (+) was suddenly withdrawn, a thermodynamic shift to passive (channel-mediated) K (+) influx was observed in barley and both species demonstrated immediate and dramatic stimulations in K (+) influx, illustrating a hitherto unexplored magnitude and rapidity of K (+) -uptake capacity and plasticity. Here, we expand on our previous work by offering further characterization of channel-mediated K (+) fluxes in intact barley, with particular focus on anion effects, root respiration and pharmacological sensitivity and highlight key additions to the current model of K (+) acquisition.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Cytokinin inhibition of leaf senescence.

  Paul J Zwack, Aaron M Rashotte
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  ABSTRACT: The senescence delaying effect of cytokinin is well known, however, the details behind how this process occurs remain unclear. Efforts to improve understanding of this phenomenon have led to the identification in Arabidopsis of specific cytokinin signaling components through which senescence signal responses are regulated. These include the cytokinin receptor (AHK3), the type-B response regulator (ARR2) and the recently identified cytokinin response factor (CRF6). At the mechanistic end of this process, it was found that increased cell-wall invertase activity which occurs in response to cytokinin is both necessary and sufficient for the inhibition of senescence. Yet, a direct link between the signaling and mechanistic steps of a cytokinin regulated senescence process has yet to be demonstrated. This may be in part because the relationship between senescence and primary metabolism implied by the key role of cell-wall invertase is the subject of two apparently opposing bodies of evidence. Here we briefly summarize and propose a model in which cytokinin mediated changes in sink/source relationships leads to delayed senescence which is consistent with existing evidence both for and against sugars as a trigger for developmental senescence.
  Plant signaling & behavior 05/2013; 8(7).
• Article: MicroFilament Analyzer identifies actin network organizations in epidermal cells of Arabidopsis thaliana roots.

  Eveline Jacques, Michal Lewandowski, Jan Buytaert, Yves Fierens, Jean-Pierre Verbelen, Kris Vissenberg
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  ABSTRACT: The plant cytoskeleton plays a crucial role in the cells' growth and development during different developmental stages and it undergoes many rearrangements. In order to describe the arrangements of the F-actin cytoskeleton in root epidermal cells of Arabidopsis thaliana, the recently developed software MicroFilament Analyzer (MFA) was exploited. This software enables high-throughput identification and quantification of the orientation of filamentous structures on digital images in a highly standardized and fast way. Using confocal microscopy and transgenic GFP-FABD2-GFP plants the actin cytoskeleton was visualized in the root epidermis. MFA analysis revealed that during the early stages of cell development F-actin is organized in a mainly random pattern. As the cells grow, they preferentially adopt a longitudinal organization, a pattern that is also preserved in the largest cells. In the evolution from young to old cells, an approximately even distribution of transverse, oblique or combined orientations is always present besides the switch from random to a longitudinal oriented actin cytoskeleton.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Salt Overly Sensitive pathway members are influenced by diurnal rhythm in rice.

  Praveen Soni, Gautam Kumar, Neelam Soda, Sneh L Singla-Pareek, Ashwani Pareek
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  ABSTRACT: The diurnal rhythm controls many aspects of plant physiology such as flowering, photosynthesis and growth. Rice is one of the staple foods for world's population. Abiotic stresses such as salinity, drought, heat and cold severely affect rice production. Under salinity stress, maintenance of ion homeostasis is a major challenge, which also defines the tolerance level of a given genotype. salt overly sensitive (SOS) pathway is well documented to play a key role in maintaining the Na (+) homeostasis in plant cell. However, it is not reported yet whether the transcriptional regulation of these genes isinfluenced by diurnal rhythm. In the present work, we have studied the diurnal pattern of transcript abundance of SOS pathway genes in rice at seedling stage.To rule out the effect of temperature fluctuations on the expression patterns of these genes, the seedlings were grown under a constant temperature. We found that OsSOS3 and OsSOS2 exhibited a rhythmic and diurnal expression pattern, while OsSOS1did not have any specific pattern of expression. This analysis establishes a cross-link between diurnal rhythm and SOS pathway and suggests that SOS pathway is influenced by diurnal rhythm in rice.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Ospapst1, a useful mutant for identifying seed purity and authenticity in hybrid rice.

  Qundan Lv, Jiming Xu, Ping Wu
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  ABSTRACT: The stability and completeness of male sterility is still a challenge in some male sterile rice lines, especially those of photoperiod/thermo-sensitive genic male sterility (P/TGMS). Leaf color marker is a widely practiced approach to reduce the impact of self-pollinated seeds of male sterile lines. The papst1 is a leaf color mutant. The newly emerged leaves of papst1 are chlorosis and have an impaired photosynthesis. But the other agronomic traits, such as germination rate, duration of maturation and seed weight, are not changed. The papst1/PAPST1 F 1 showed the wild-type leaf phenotype. The papst1/PAPST1 F 2 progenies displayed an approximately 3:1 segregation ratio of WT phenotype:mutant phenotype (72: 28, χ ( 2) = 0.48, p > 0.05), suggesting that papst1 mutant phenotype is caused by a single repressive gene. Map-based cloning and sequencing analysis revealed that a point mutation was occurred in Os01 g16040 (OsPAPST1). Given these results, the Ospapst1 mutant is a useful mutant for identifying seed purity and authenticity in hybrid rice.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Emerging role of SUMOylation in plant development.

  Panglian Xu, Chengwei Yang
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  ABSTRACT: Post-translational attachment of small ubiquitin-like modifier (SUMO), defined as SUMOylation, has emerged as a new mechanism of protein regulation in plant biology. In plant, SUMOylation has been shown to play crucial roles in a variety of biotic and abiotic stress responses. Recent work using viable mutants with defective SUMOylation have indicated an important role for SUMOylation in a wide range of developmental processes, such as cell division, expansion, survival and differentiation, vegetative growth and reproductive development. This review will summarize the currently emerging information regarding the function of SUMOylation in plant development.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Architectural remodeling of the tonoplast during fluid-phase endocytosis.

  Ed Etxeberria, Pedro Gonzalez, Javier Pozueta-Romero
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  ABSTRACT: During fluid phase endocytosis (FPE) in plant storage cells, the vacuole receives a considerable amount of membrane and fluid contents. If allowed to accumulate over a period of time, the enlarging tonoplast and increase in fluids would invariably disrupt the structural equilibrium of the mature cells. Therefore, a membrane retrieval process must exist that will guarantee membrane homeostasis in light of tonoplast expansion by membrane addition during FPE. We examined the morphological changes to the vacuolar structure during endocytosis in red beet hypocotyl tissue using scanning laser confocal microscopy and immunohistochemistry. The heavily pigmented storage vacuole allowed us to visualize all architectural transformations during treatment. When red beet tissue was incubated in 200 mM sucrose, a portion of the sucrose accumulated entered the cell by means of FPE. The accumulation process was accompanied by the development of vacuole-derived vesicles which transiently counterbalanced the addition of surplus endocytic membrane during rapid rates of endocytosis. Topographic fluorescent confocal micrographs showed an ensuing reduction in the size of the vacuole-derived vesicles and further suggest their reincorporation into the vacuole to maintain vacuolar unity and solute concentration.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Effect of external and internal factors on the expression of reporter genes driven by the N resistance gene promoter.

  Palak Kathiria, Corinne Sidler, Rafal Woycicki, Youli Yao, Igor Kovalchuk
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  ABSTRACT: The role of resistance (R) genes in plant pathogen interaction has been studied extensively due to its economical impact on agriculture. Interaction between tobacco mosaic virus (TMV) and the N protein from tobacco is one of the most widely used models to understand various aspects of pathogen resistance. The transcription activity governed by N gene promoter is one of the least understood elements of the model. In this study, the N gene promoter was cloned and fused with two different reporter genes, one encoding β-glucuronidase (N::GUS) and another, luciferase (N::LUC). Tobacco plants transformed with the N::GUS or N::LUC reporter constructs were screened for homozygosity and stable expression. Histochemical analysis of N::GUS tobacco plants revealed that the expression is organ specific and developmentally regulated. Whereas two week old plants expressed GUS in midveins only, 6-wk-old plants also expressed GUS in leaf lamella. Roots did not show GUS expression at any time during development. Experiments to address effects of external stress were performed using N::LUC tobacco plants. These experiments showed that N gene promoter expression was suppressed when plants were exposed to high but not low temperatures. Expression was also upregulated in response to TMV, but no changes were observed in plants treated with SA.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Separation anxiety: An analysis of ethylene-induced cleavage of EIN2.

  Bret Cooper
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  ABSTRACT: Since the discovery of the CTR1 protein kinase and the endoplasmic reticulum (ER)-localized EIN2 protein nearly 20 y ago, plant biologists have wondered how these proteins respectively serve as negative and positive regulators of ethylene-mediated signal transduction in plants. ( 1) (,) ( 2) Now with the publication of four studies, it can be concluded that in the absence of ethylene (ET) in Arabidopsis thaliana, CTR1 phosphorylates EIN2 thereby inactivating ET signal transduction, while in the presence of ET, CTR1 no longer phosphorylates EIN2 and the cytosolic C-terminus of EIN2 is released from the ER to translocate to the nucleus to promote gene transcription. ( 3) (-) ( 6) Chen et al. (2011) showed that EIN2 is differentially phosphorylated at amino acids (a.a.) S ( 645) and S ( 924) after ET treatment. ( 6) Ju et al. (2012) then proved that CTR1 phosphorylates EIN2 at those positions and that the lack of phosphorylation at S ( 645) and S ( 924) leads to the translocation of an EIN2 C-terminus peptide. ( 5) Wen et al. (2012) and Qiao et al. (2012) also demonstrated ET-induced translocation of an EIN2 C-terminus peptide, while Qiao et al. (2012) proved that EIN2 has a nuclear localization signal sequence required for translocation, confirmed phosphorylation at S ( 645) and said that proteolytic cleavage occurs at S ( 645) in absence of phosphorylation there. ( 3) (,) ( 4) Despite the revelation of this elegant switch, there are contradictory indications for specific cleavage at EIN2 S ( 645) . This article investigates the data and concludes that EIN2 may be cleaved at alternative positions.
  Plant signaling & behavior 05/2013; 8(7).
• Article: Distinct salt-dependent effects impair Fremyella diplosiphon pigmentation and cellular shape.

  Shailendra P Singh, Beronda L Montgomery
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  ABSTRACT: Salt impairs cellular morphology and photosynthetic pigment accumulation in the cyanobacterium Fremyella diplosiphon. Recent findings indicated that the impact of salt on cellular morphology was attributable to salt-associated effects on osmotic regulation, as the impact on morphology was reversible when cells were treated with an osmoticum in the presence of salt. The impact of salt on photosynthetic pigment accumulation was associated with ionic effects of salt on the cells, as pigment levels remained low when salt-treated cells were incubated together with an osmoticum or an antioxidant, the latter to mitigate the impact of a salt-associated accumulation of reactive oxygen species. Here, we provide evidence that the transcripts for genes encoding the phycobiliproteins are not reduced in the presence of salt. These results suggest that the negative impact of salt-mediated changes on pigment accumulation occurs post-transcriptionally. A greater understanding of the mechanisms which impact growth of strains such as F. diplosiphon, which harbor pigments that allow low-light and shade-tolerated growth, may facilitate the development or adaptation of such strains as useful for remediation of salt-impacted soils or biofuel production.
  Plant signaling & behavior 05/2013; 8(7).